Encapsulated vacuum insulated circuit breaker



Jan. 20, 1959 H. H. SCHWAGER 2,870,293 ENCAFSULATED VACUUM INSULATED CIRCUIT BREAKER Filed Aug. 2?, 195s IN V EN TOR. AQMYHSKHWAQER.

United States Pater fifice Patented Jan.

EN CAPSULATED VACUUM INSULATED CIRCUIT BREAKER Henry H. Schwager, Portland, Oreg., assignor to Schwager-Wood Corporation, Portland, ore a corporation of Oregon Application August 27, 1956, Serial No. 606,265

2 Claims. 01. 200-144 My present invention relates to .high voltage circuit interrupting devices and more particularly to an improvement in vacuum insulated high voltage circuit breakershaving circuit controlling contacts enclosed in a fragile vacuum supporting envelope.

The main object of this invention is to provide a new and novel improvement in the form of a reinforcing encapsulation for vacuum insulated circuit breakers of the type having exposed line terminals and cooperating contacts enclosed within an evacuated fragile envelope which will make possible the mounting and practical use of these circuit breakers in outdoor installations, such as in outdooor power distribution sub-stations and for'switching operations along high voltage power transmission lines.

Another object of the invention is to provide an encapsulation .for vacuum insulated switches which will protect-the fragile vacuum supporting envelope in such a manner that the switch will be protected against mechanical shocks and strains and/ or breakage due to forces imposed upon the exposed terminals thereof under conditions to be found in connection .with their use in and along high voltage outdoor power transmission circuits.

There has been on the'market many different types of vacuum insulated switches for low voltage industrial uses and more recently, it has'been found that these vacuum insulated switches can be constructed and designed to operate as circuit breakers under the voltage and current conditions presently found in outdoor power distribution systems for the transmission of electric power from re mote generating stations and over long distances. A major requirement for a vacuum insulated switch of this character is that the extremely high vacuum by which the operating contacts thereof are insulated must be maintained. In practice, the contacts of these switches are therefore enclosed in an evacuating glass envelope. Because of this requirement and the need for external circuit connections the unit is of an extremely fragile nature. This is a detriment to the use of these switches in many instances where they are mounted in position upon a circuit by the terminals thereof and the mechanical operation thereof may subject the enclosing envelope to shocks and stresses which might rupture the glass and/ or break the terminal seals at the ends thereof and thus render the switches inoperative due to a loss of the insulating vacuum surrounding the contacts.

It is, therefore, a further object of my invention to provide an improvement which will greatly enlarge the usefulness of these vacuum insulated switches by encapsulating the vacuum maintaining envelope with a mechanically strong reinforcing, shock resisting and weather resistant material such for example; with a suitable thermo-setting or cold setting casting resin such as an epoxy resin or any other material suitable for this duty which will eliminate the inherent draw backs mentioned above.

Other objects and advantages of my invention will be in part evident to those skilled in the art and in part pointed out in connection with the accompanying draw ing, wherein there is shown by way of illustration and not of limitation a preferred embodiment of the invention.

In the drawing wherein like numerals refer to like parts throughout the several views;

Figure 1 is a vertical view in half section, with parts broken away to reveal the details of one type of a vacuum insulated switch encapsulated in accordance with one embodiment of the invention, and

Figure 2 is a half section showing the vacuum switch of Fi ure l as encapsulated in accordance with another embodiment of the invention.

For the purpose of illustration and description, I have in the accompanying drawing shown my invention in connection with a vacuum switch of the type illustrated and described in United States Patent No. 2,740,869 issued April 3, 1956, to lo E. Jennings, and entitled Vacuum Switch.

It is contemplated that my invention will find use with many other types of vacuum insulated switches, however, the switch here shown has been found to operate very satisfactorily under the voltage and current condi tions found to exist along high voltage power transmission lines and other outdoor installations such as in feeder line controlling sub-stations and where an encapsulation such as is here proposed performs a useful pu pose. In other words, the particular vacuum switch shown is for illustrative purposes only and forms no part of my present invention except insofar as its fragile construction requires and lends itself to the particular form of the encapsulation here detcribed. It, therefore, seems only necessary to point out that as shown in the drawing, this particular vacuum switch has a stationary contact 10 that is connected directly to a closure cap it having a terminal contact ring 12, at the uppper end of the switch. in axial alignment with the stationary contact 10, there is a movable contact 13 which is connected through an end closure cap 14 to a second terminal contact ring 15 at the bottom of the unit. In this particular arrangement, the relatively movable contacts 1%) and 713 are shown as enclosed within an evacuated glass envelope that is closed at its ends by he aforesaid metallic caps 11 and 14. To permit the required circuit controlling movements of the movable contact the lower end of the evacuated envelope 16 is shown sealed by a flexible bellows 17 which as is well understood will permit movement of the contact 13 toward and away from the stationary contact 16} without danger of breaking the vacuum seal of the envelope 1'6. This movement of the contact 13 is accomplished through the medium of an extending stud 18 which has a sliding fit through the closure cap 4, at this end of the evacuated envelope 16. The vacuum switch also has a baffie or shield 19 surrounding the point of separation be tween the contacts 10 and 13 and functions in part to dissipate heat and prevent the deposit of vaporized contact metal upon the inside surface of the envelope 16 which might destroy or reduce the effective life of the switch.

Upon closer examination, it will be noted that the evacuated glass portion of the envelope 16 is complete at each of its ends by fusion with the metallic caps 11 and 14 respectively at the upper and lower ends of the switch. The seal between the metal caps 11 and 14 and the glass body of the envelope 16 is of the so-called housekeeper type in which the metal is drawn out to a feather edge for fusion with the glass at the seal. While such a seal is effective in maintaining the required vacuum within the evacuated envelope 16, these seals constitute a point of weakness which in addition to the fragile nature of the glass renders the vacuum switches constructed in this manner unsuited to the rugged operating conditions found on high voltage outdoor power line installations. In this field of use the operating mechanism with which a vacuum switch of this character might be used will be of considerable size and because of the allowable tolerances in construction and the contact pressures involved, the usefulness of such a vacuum switch, without some means to reinforce and otherwise improve upon its construction, would be limited.

To overcome the dilliculties presented in the use of vacuum insulated switches of the character here shown on outdoor installations and make possible their use as a high voltage circuit breaker along a power transmission line or in an outdoor sub-station, I have in Figure 1 of the drawing, shown the envelope 16 as surrounded and/ or encapsulated within an outer shell 20. This shell 20 may be of solid non-elastic insulating material such as a cold setting plastic resin compound having sufficient mechanical strength to stand up under the mechanical strains, stresses and shocks which are normally encountered in the proposed field of use. To insure against flash-overs, I have shown the encapsulating shell 20 as having axially spaced annular skirt-like extensions 23 formed in the manner commonly employed upon outdoor power line supporting insulators.

In the modification of my invention as shown in Figure 2 of the drawing, the encapsulating shell here designated by the numeral 21 extends over the exposed end caps 11 and 1d of the vacuum switch. In this arrangement, the terminal contact rings 12 and 15 have been omitted and the closure cap 11 is shown as having an extending stud 22 through which circuit connections may be made at this end of the switch. At the lower end of the switch, the movable contact control rod 18 which controls the movements of the movable contact 13 serves as the other ci cuit completing terminal of the switch. In this particular embodiment of my invention the encapsulating shell 21 is formed with a cylindrical portion 24 intermediate its ends which may be encircled by a clamping band 25 of a form suitable for attachment to any support upon which it may be desired to mount the switch.

While it is conceivable that the encapsulating shells 20 and 21 described above may be of any suitable material having the required strength and electrical insulating and weather resisting qualities, I have found that good results may be obtained by forming the encapsulating shells 2t) and 21 of an epoxy resin of the casting type now on the market. Two such casting resins known as Epon 820 and Epon 828 are manufactured and sold by the Shell Chemical Corporation. This material has excellent insulating quality and great mechanical strength and can be cast over the switch as an encapsulation in any suitable manner, as for example, by merely providing a confining mould within which the switch unit is positioned as a core for the casting.

While I have, for the sake of clearness and in order to disclose my invention so that the same can be readily understood, described and illustrated a specific form and arrangement, I desire to have it understood that this invention is not limited to the specific form disclosed, but may be embodied in other ways that will suggest themal selves to persons skilled in the art. It is believed that this invention is new and all such changes as come within the scope of the appended claims are to be considered as part of this invention.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. In a circuit interrupting switch for high voltage power transmission lines, the combination of an evacuated cylindrical envelope of glass, coextending terminal supporting metallic caps secured at the ends of said envelope by housekeeper seals, an annular line terminal forming flange carried by each of said metallic caps disposed axially outward beyond said seals and extending in planes trans verse to the axis of said envelope, a stationary circuit controlling contact supported within said envelope by one of said metallic caps, a relatively movable circuit con trolling contact supported by and extending through the other of said metallic caps, and a rigid member of an insulating compound cast over said envelope between said terminal forming annular flanges operating as a weather protective encapsulation for said envelope and as a reinforcing stress and strain sustaining support for the line terminal forming annular flanges carried by said metallic caps.

2. In a circuit interrupting switch for high voltage power transmission lines, the combination of an evacuated cylindrical envelope of glass, coextending terminal supporting metallic caps secured at the ends of said envelope by housekeeper seals, an annular line terminal forming flange carried by each of said metallic caps beyond said seals and extending outwardly in planes transverse to the axis of said envelope, a stationary circuit controlling contact supported within said envelope by one of said metallic caps, a relatively movable circuit controlling contact supported by and extending through the other of Said metallic caps, and an epoxy resin compound cast over said envelope and said housekeeper seals and engaging the terminal forming annular flanges carried by said metallic caps operating as a weather protective encapsulation for said envelope and as a reinforcing stress and strain sustaining support for the line terminal forming annular flanges carried by said metallic caps.

References Cited in the file of this patent UNITED STATES PATENTS 1,770,130 Dunrnire July 8, 1930 1,972,362 Sovensen Sept. 4, 1934 2,222,729 Planck et al. Nov. 26, 1940 2,683,767 Cunningham July 13, 1954 2,706,742 Ehlers Apr. 19, 1955 2,740,869 Jennings Apr. 3, 1956 2,773,154 Williams Dec. 4, 1956 FOREIGN PATENTS 569,123 Germany Jan. 30, 1933 615,965 Germany July 17, 1935 OTHER REFERENCES Ethoxylines; Modern Plastics, November 1950; pages -88. 

